Subjective Cognitive Effort Indexes Sub-Criticality in the Brain

项目摘要 认知方面的努力在主观上是昂贵的。它会导致人们忽视有价值的目标，避免深思熟虑的计划和仔细的深思熟虑。因此，努力回避可能是有问题的，特别是在抑郁症和精神分裂症等疾病中，过度的成本敏感性会破坏认知动机。为了解决成本敏感性问题，我们首先需要了解大脑认为什么是成本。传统的指标，如侧额叶功能磁共振成像信号和脑电数据中的顶叶阿尔法去同步，会追踪认知负荷到某一点，但往往是持平或下降，即使主观努力继续上升。这个项目将考察主观认知努力体验背后的一个有希望的候选机制：偏离临界性。临界性是休息时皮质动力学的特征，先前的研究表明，在已知会增加主观努力的情况下，大脑变得越来越亚临界性：工作记忆负荷增加、疲劳、睡眠不足、新鲜感和认知老化。在申请者的K99训练阶段，他们发现大脑动力学偏离了一个临界点，任务变得越困难。然而，最重要的是，大脑偏离这一临界点最多的人认为，与大脑更接近临界点的人相比，他们在主观上更容易完成任务。据推测，接近临界点取决于皮层兴奋性信号和抑制性信号的平衡。与这一假设一致的是，申请人还发现，使用经颅磁刺激来人为干扰皮质兴奋性也会使大脑远离临界点，并增加后续认知任务的主观努力。然而，经颅磁刺激效应的方向令人惊讶，这为从临界动力学角度研究经颅磁刺激对脑功能的影响打开了新的假设之门。这个项目将测试一种假设，即皮层兴奋抑制平衡调节大脑运行到临界状态的程度，从而调节人们对努力成本的敏感程度。在这样做的同时，该项目还将重新检查常见的经颅磁刺激方案对关键、亚临界和超临界动力学方面的皮质兴奋性的影响。因此，目标1将结合脑电和经颅磁刺激来测试可能构成认知努力、工作记忆和认知动机的假想机制，并重新评估关于经颅磁刺激对皮质可塑性影响的长期假设。

Project Summary Cognitive effort is subjectively costly. It can cause people to discount valuable goals and avoid thoughtful planning and careful deliberation. Effort avoidance can thus be problematic, especially in disorders like depression and schizophrenia where excessive cost sensitivity undermines cognitive motivation. To address cost sensitivity, we first need to understand what the brain treats as costly. Traditional indices, like lateral frontal functional magnetic resonance imaging signals, and parietal alpha desynchronization in electroencephalography data, track cognitive load to a point, but often plateau or decline, even when subjective effort continues to rise. This project will examine a promising candidate mechanism underlying the experience of subjective cognitive effort: divergence from criticality. Criticality characterizes cortical dynamics at rest, and prior studies have shown that brains become increasingly sub-critical under the very conditions known to increase subjective effort: increasing working memory load, fatigue, sleep deprivation, novelty, and cognitive aging. In the Applicant’s K99 training phase, they found that brain dynamics diverge from a critical point, the harder that tasks become. Most importantly, however, people whos’ brains diverge the most from that critical point experience tasks as more subjectively effortful than people whos’ brains more closely approximate criticality. It is hypothesized that proximity to a critical point depends on the balance of cortical excitatory versus inhibitory signaling. Consistent with this hypothesis, the Applicant also found that artificially perturbing cortical excitability using transcranial magnetic stimulation also pushes brains farther away from a critical point and increases subjective effort on a subsequent cognitive task. The direction of the effect of transcranial magnetic stimulation was surprising, however, opening doors to new hypotheses about the effects of transcranial magnetic stimulation on brain function from the perspective of critical dynamics. This project will test the hypothesis that the cortical excitatory inhibitory balance regulates how closely to a critical state the brain operates, and thereby how sensitive people are to effort costs. In so doing, the project will also re-examine the effects of common transcranial magnetic stimulation protocols on cortical excitability with respect to critical, sub-critical, and super-critical dynamics. Thus, Aim 1 will combine electroencephalography and transcranial magnetic stimulation to test hypothesized mechanisms which may underlie cognitive effort, working memory, and cognitive motivation and also re-assess longstanding assumptions about the effects of transcranial magnetic stimulation on cortical plasticity.